At present, the average life-span in China is over 70 years old. Predicted by a scientific research abroad, by year 2025 there will be 18.8% persons over 65 years old. This data indicates that, 20 years later, there will be one elder in every 5 people. Alzheimer's Disease tends to occur in people older than 50 years. Multi-infarct dementia or senile dementia due to cerebrovascular pathological changes occurs in people older than 60 years. As the world's population grows older, the incidence of Alzheimer's Disease and Senile Dementia is expected to increase. The ageing and the peculiar neurological degenerative diseases-different kinds of dementia will go through two types of death, first in spirit, then in physical. It does not only afflict the patients, but also brings burden to their families and the society. The aging population is considered to be an adverse factor impacting social development and stability, only inferior to battles, plague, starvation and shortage in resource.
Dementia is an acquired and durative intellective obstacle syndromes caused by brain function impediment that includes cognitive decline, impaired memory, language, thinking, behaviour, and abnormal personality. Dementia mainly includes Alzheimer's Disease, Vascular Dementia, and etc. The pathological changes of Alzheimer's Disease involve the formation of senile plaques-mostly made of a component called Aβ (β-amyloid peptide), the loss of cholinergic neurons and the deposition of Aβ in endotheliocyte of the blood vessels, etc. Vascular Dementia is induced by cerebrovascular diseases, mostly ischemia. The pathological changes involve multiple lacunae illness or large-scale infarct and atherosclerotic changes. Recent studies indicate that vascular factors participate in the process of Senile Dementia and the lack of blood flow in brain is the most risky factor.
There are many kinds of drugs for preventing ageing and treating Senile Dementia. At present, the leading remedies applied clinically are cholinergic drugs and Acetylcholinerase inhibitors (ChEIs), accompanied with adjuvant treatment on improvement of cerebrovascular circulation and protection of brain, yet the effect is limited. Among the drugs increasing cholinergic system function, only Ach precursor show mild therapeutical effect. Although Ach receptor agonists and ChEIs have certain effects, the duration is too short and the adverse effects are relatively great. Cerebrovascular dilation drugs help in energy supply and intellectual improvement by enhancing the brain blood supply, but the really valuable drugs for cerebrovascular dilation must have high selectivity, meanwhile, they will not affect brain metabolism and ‘pilfer blood’, and they have anti-aggregating of blood platelet and anti-thrombus effect. Nimodipine, a Calcium antagonist, qualifies some of the above criteria, but it only acts on L-type voltage-gated Ca2+ channel and has no effects on N-type and T-type Ca2+ channels. Some neuropeptides and NGF were deemed to be promising in the treatment of dementia, but their clinical trail results were discouraging, primarily attribute to be hard to pass the blood-brain barrier (BBB) and exert their actions in brain. Since 2-pyrrolidone acetamide (trade name Piracetam) came into use, there is no doubt that it is a new nootropic in the early reports. It is recently reported at home and abroad, it has mild effect or does not act on all kinds of memory impairments and senile dementia. It is a water soluble compound and has a low permeance through BBB, and it is difficult to be concentrated to the target to exert its effect.
Coeloglossum viride (L.) Hartm. Var. bracteatum (Willd.) Richter is widely distributed, mainly in the west of China such as Tibet, Inner Mongolia, Shanxi, Gansu, Qinghai, etc. The dried rhizome of Coelogrlossum viride (L.) Hartm. var. bracteatum is the famous Tibetan medicine named Wangla, having a long history of use in minority in the west of china. The indications were multiple, such as invigorating vital energy, promoting the production of body fluid, tranquilizing and enhancing intelligence.
Through the preliminary biological activity screening of this plant, we found that the ethanolic extract of the rhizome of this plant has preferable intellectual improvement, sedation and anti-fatigue activities, which is consistent with its indications. Based on the results, we investigated systematically the chemical component and biological activity of this plant, and several derivatives of succinate mono- and di-esters were isolated and identified. The chemical components of Coeloglossum viride (L.) Hartm. var. bracteatum (Willd.) Richter have been published by the inventors, but the biological activities of the extract and purified compounds have not been reported. (See: Huang Sheng-Yang, Shi Jian-Gong, Yang Yun-Chun, Hu Shi-lin, Studies on the Chemical Constituents of Coeloglossu viride (L) Harm. var. bracteatum (Willd) Richter., Acta Pharmaceutica Sinica, 2002, 37(3), 199-203; Sheng Yang HUANG, Jian Gong SHI, Yong Chun YANG, Shi Lin HU. Two new isobutyltartrate monoesters from Coeloglossum viride (L.) Hartm. var. bracteatum (Willd.) Richter. Chinese Chemical Letters, 2002, 13(6):551-554.)